Sorry, but that is not possible with FaceTime. A FaceTime call is one to one, not one to many. There is no way to confernece call or group call with FaceTime. FaceTime supports group chats, but not group video conferencing.
You would need to find a third party app for that (Skype, Viber, Google Duo (replaces hangouts) for example).
You also cannot use a single AppleID with all those people for FaceTime - you cannot call yourself. And sharing an AppleID will only create many other headaches of merged, mixed and messed up shared data. Everyone should have their own AppleID for all Apple services (iMessage, FaceTime, iCloud, iTunes, App and iBook Stores, etc). You can use family sharing to share content from iTunes or the App stores.
For iMessage, they just need to create a group - Send a group message on your iPhone, iPad, or iPod touch - Apple Support